BG67304B1 - Electric machine with additional movable stator - Google Patents

Abstract

The electric machine has a double magnetic stator. One part of the stator (1) is attached to the motor housing (4), and the second part of the stator (6) can rotate freely around a rotor shaft (3). The movable stator (6) is passively oriented according to the lines of the magnetic field created by electric winding coils and / or the permanent magnets of the fixed stator (1). The movable stator (6) concentrates and shapes the magnetic field B so that the magnetic lines are almost perpendicular to the rotor coil windings. The movable stator (6) does not rotate relative to the magnetic field of the fixed stator (1) and does not change the magnetic field therein, further does not receive continuous magnetic reversal, and magnetic hysteresis is avoided and does not generate eddy currents, thus reducing losses and heating of the machine. The movable stator (6) does not rotate relative to the magnetic field of the fixed stator (1) and permanent magnets can be used therein in order to amplify the magnetic field B in the active zones of the rotor (2).

Description

Field of technology

The present invention relates generally to electrical machines designed to convert energy through the use of electromagnetic induction. In particular, the present invention relates to a method of directing the magnetic field by adding to the stator and rotor of the machine an additional self-directing element called a movable stator.

BACKGROUND OF THE INVENTION

Each rotating electric machine has a stator and a rotor separated by an air gap. The majority of electrical machines manufactured at the time of filing the present patent application use a magnetic field to transmit energy between the stator and the rotor and to convert the electrical energy into mechanical motion. In generator mode, the reverse conversion occurs - the magnetic field generates an electric current in the windings. In any electrical machine, the direction of energy conversion can be changed, ie they can convert mechanical energy into electrical (generator mode) or electrical energy into mechanical (motor mode). The active parts of the machine are the magnetic circuit and the windings in which the energy is converted. Energy conversion losses generate heat. A cooling system is used to keep the temperature within acceptable limits.

When calculating the electromotive moment, the Lorentz force or the force of repulsion / attraction between identical / opposite magnetic poles is applied. In both cases, the direction and magnitude of the magnetic field are crucial. The magnetic field is generated by permanent magnets and / or electromagnets of the stator and the rotor is located inside this magnetic field. All materials located between the magnetic poles of the stator affect the distribution of the magnetic field, ie air gaps and holes, ferromagnetic and paramagnetic materials redirect the magnetic lines and form regions with different direction and magnitude of the magnetic field.

In order to achieve the maximum magnetically moving voltage and, accordingly, the maximum torque and efficiency, you must:

- when using Lorentz force - the conductors of the windings must be perpendicular to the lines of the magnetic field and, accordingly, the magnetic field must be concentrated in the area of electric current flow in the windings;

- when using permanent magnets or electromagnets in the rotor - the magnetic lines must pass along the tangent of the rotor and push the rotor magnets in the direction of rotation of the rotor. Accordingly, in these areas the stator magnetic field must be maximum.

The same conditions apply when the electric machine is operating as a generator and the highest electromotive voltage must be achieved.

To achieve these goals, combinations of different materials are used in the rotor and it is shaped in such a way that at whatever angle the rotor is rotated, the magnetic field has an "acceptable" shape. This is a serious problem because the "insensitivity" of the magnetic field to the angle of rotation of the rotor and the concentration of the magnetic field are mutually contradictory tasks.

BG 67304 Bl

The rotation of the magnetic circuit (as part of the rotor) leads to the generation of eddy currents in the magnetic circuit. To reduce this problem, the rotors are made of metal plates (lamellae), extruded ferrite powder or are hollow (eg an executive DC motor with a hollow non-magnetic anchor). This increases the cost of the motors because it complicates the construction of the rotor. In the case of a hollow non-magnetic armature motor, the scattering of the magnetic field greatly degrades the characteristics of the motor and such motors are used only when high speed is required.

The DC motor with a hollow non-magnetic armature is considered to be one of the fastest with a time constant of a few milliseconds, as the rotor has a small mass, a small moment of inertia and a small time constant.

Technical essence of the invention

The electric machine according to the invention comprises a fixed stator and a rotor mounted in the stator, fixed to the rotor shaft, using magnetic induction to transfer energy between the stator and the rotor. According to the invention, the rotor is hollow and at least one additional movable stator is arranged inside it co-rotatably, adapted to orient itself to the magnetic field generated by the machine, being made at least partially of ferromagnetic materials and mounted to the rotor shaft with possibility for free rotation around it and, respectively, relative to the rotor.

In one embodiment, the ferromagnetic material in the at least one movable stator forms a body passing through the geometric axis of the movable stator and having an elongated profile in cross section extending between two diametrically opposite zones on the periphery of the movable stator.

It is possible for the ferromagnetic material in at least one movable stator to form two or more even numbers of bodies, each of these bodies being identical in shape and located symmetrically with respect to the axis of rotation and diametrically opposite each other on the periphery of the movable stator.

Preferably, the ferromagnetic part of the at least one movable stator is made at least in part of permanent magnets. Even more preferably, the ferromagnetic part of the movable stator is made entirely of permanent magnets.

It is possible that at least one movable stator is partially made of paramagnetic materials outside the areas with ferromagnetic material.

It is desirable that the fasteners of at least one movable stator be made of paramagnetic materials.

It is possible for the rotor to be a hollow cylinder located between the stator and the movable stator. Alternatively, the rotor may be a hollow cone located between the stator and the movable stator. It is also possible for the rotor to be disk-shaped, located between the stator and the movable stator.

It is possible for an electric machine to have more than two magnetic poles.

The movable stator may contain permanent magnets and parts made of ferromagnetic and paramagnetic materials. The movable stator is designed to direct the magnetic lines of the magnetic field generated by the stator so that the magnetic lines are perpendicular to the rotor windings. The movable stator is oriented relative to the poles of the magnetic field generated by the stator, just as the compass needle is oriented relative to the earth's magnetic field. Since the movable stator does not move relative to the magnetic field, the ferromagnetic material is magnetized and a weak magnet is formed. The movable stator is always located in

BG 67304 Bl is the same position with respect to the magnetic field generated by the stator and there is no need for the movable stator to conduct a magnetic field in all directions.

Less material is needed to make the rotor together with the movable stator compared to the material needed for the rotor of existing machines, so the machine becomes lighter.

No eddy currents are generated in the movable stator because it is stationary relative to the magnetic field generated by the stator, so it does not have to be made of plates or use other techniques to reduce heating and eddy current losses. Ferromagnetic materials are magnetized, and their domains are oriented in the direction of the magnetic lines. Since the movable stator is stationary relative to the magnetic field generated by the stator, reorientation of the domains, loss of energy required for this process and overheating generated by re-magnetization are avoided. When the ferromagnetic material of the rotor of existing machines becomes a weak magnet, the rotor tends to remain oriented in the direction of the magnetic lines and part of the generated magneto-driving voltage must overcome this resistance - this leads to a reduction in efficiency.

The use of ferromagnetic materials to make the movable stator generally simplifies the design of the machine and reduces losses in it. Performance is improved, but does not differ significantly from the performance of existing machines. When permanent magnets are used in the movable stator, the magnitude of the magnetic field generated in the rotor region is increased because the magnetic fields of the stator and the permanent magnets of the movable stator are summed. In this way, the torque of the electric machine is increased, because the Lorentz force and hence the power output is directly proportional to the magnetic field in the field of the rotor windings.

Explanation of the attached figures

In more detail, an electric machine according to the invention is illustrated by preferred embodiments, given as a non-limiting example, with reference to the accompanying figures, where:

Figure 1 shows a simplified longitudinal top view of a collector DC motor.

Figure 2 is a cross section of a machine with a stator 1 represented by two permanent magnets N and S. The movable stator 6 made of paramagnetic material is not shown to see the shape of the magnetic field obtained from the two magnets N and S of the fixed stator 1.

Figure 3 shows the magnitude of the magnetic field along the contour AA of the machine of Figure 2.

Figure 4 is a cross-section of a machine with a stator 1 represented by two permanent magnets N and S. The movable ferromagnetic stator 6 is in the form of a solid cylinder.

Figure 5 shows the magnitude of the magnetic field along the contour AA of the machine of Figure 4.

Figure 6 is a cross section of a machine with a stator 1, represented by two permanent magnets N and S. The movable stator 6 is composed of two parts - ferromagnetic 7 and internal paramagnetic.

Figure 7 shows the magnitude of the magnetic field along the contour AA of the machine of Figure 6.

Figure 8 is a cross section of a machine with a stator 1 represented by two permanent magnets N and S. The movable stator 6 is made of a dense ferromagnetic material.

Figure 9 shows the magnitude of the magnetic field along the contour AA of the machine of Figure 8.

BG 67304 Bl

Figure 10 is a cross section of a machine with a stator 1, represented by two permanent magnets N and S. The movable stator 6 is composed of two parts - a permanent magnet 7 and an internal paramagnet.

Figure 11 shows the magnitude of the magnetic field along the contour AA of the machine of Figure 10.

Figure 12 is a cross section of a machine with a stator 1, represented by two permanent magnets N and S. The movable stator 6 is composed of two parts - a permanent magnet 7 and a ferromagnet 8.

Figure 13 shows the magnitude of the magnetic field along the contour AA of the machine of Figure 12.

Figure 14 is a cross-section of a machine with a stator 1 represented by two permanent magnets N and S. The movable stator 6 is an integral permanent magnet.

Figure 15 shows the magnitude of the magnetic field along the contour AA of the machine of Figure 14.

An example of an embodiment and operation of the invention

The present invention is applicable to various types of electrical machines operating in generator or motor mode. For example, DC motors, asynchronous motors, etc. Although the invention is applicable to different types of motors and generators, the figures show a collector DC motor to explain the idea, which is the same for all electrical machines. The attached figures do not exhaust all possible configurations.

Existing electrical machines consist mainly of two parts that move relative to each other. One part is attached to the housing 4 of the machine and is called the stator 1. The other part moves relative to the stator and is called the rotor. The rotor is attached to the shaft of the machine, which thanks to bearings 5 can rotate freely. There is an air gap 14 between the rotor and the stator. The energy transfer between the stator and the rotor takes place by means of the magnetic field B created by the machine.

The present invention adds a third part of the machine that can rotate relative to both the stator and the rotor.

According to the present invention, the rotor of existing electrical machines is divided into two parts - an active part, hereinafter referred to as a rotor, where the magnetic elements, such as permanent magnets or electrical windings, and a magnetic conductor part, hereinafter referred to as a movable stator. There is an air gap 15 between the rotor and the movable stator 6.

Figure 1 shows a simplified longitudinal top view of a collector DC motor. Only the construction of the stators and rotor is shown. The collectors are not shown in the figure as they have no relation to the invention. The fixed stator is attached to the motor housing 4. (Fasteners are not shown.) The bearings 5 allow the shaft 3 to rotate freely about the 0-0 axis. The hollow rotor 2 is fastened to the shaft 3 by means of the fastening elements 13 and rotates together with it. Inside the rotor 2 is a movable stator 6, which consists of an outer part 7, an inner part 8 and fasteners 9. The inner part 8 of the movable stator 6 is separated from the shaft 3 by an air gap 16. The movable stator 6 is mounted to the shaft 3 of the machine by means of bearings 5 and can rotate freely about the axis of rotation of the rotor 2. In this way the movable stator 6 can change its orientation relative to both the rotor 2 and the stator 1. To the left of figure 1 are shows the areas occupied by the individual parts of the machine - the shaft 3, the movable stator 6, the rotor 2 and the fixed stator 1, representing nested cylinders separated by air gaps. The rotor 2 is separated from the fixed stator 1 and the movable stator 6 by air gaps 14 and 15. In this way, the fixed stator 1, the rotor 2 and the movable stator 6 can rotate freely relative to each other. The rotor

BG 67304 Bl package 11 is located and moves between the stator magnets 1 and the outer part 7 of the movable stator 6. The armature winding 12 and the fastening elements 13 of the rotor 2 are located outside the area closed between the stator magnets 1 and the outer part 7 of the movable stator. stator 6.

The rotor of the machine can be a hollow cylinder, a hollow cone or be disk-shaped. The movable stator 6 can have different shapes, which must correspond to the rotor cavity, respectively it can be cylindrical, conical or disk-shaped, as well as part of a cylinder, part of a cone, part of a disk, etc.

Figures 2, 4, 6, 8, 10, 12 and 14 show cross-sections in the plane C-C of different configurations of the DC motor of Figure 1. From the stator 1 only the two magnets 10 are shown. The rotor 2 is not shown, to see the magnetic lines more clearly. The shaft 3 of the machine together with the rotor 2 rotate about the axis O-O, which is perpendicular to the shown section C-C. The movable stator 6 must be made at least in part of ferromagnetic material. The movable stator 6 can also be made of various materials - paramagnetic (in their place there may be air), ferromagnetic (for example, anode iron) and permanent magnets of the same type as the magnets 10 of the fixed stator 1. The individual parts are not shaded to see the magnetic lines more clearly. The same geometric dimensions are used to correctly compare the results of the simulations in the static position of the depicted parts of the machine.

For example, in Figure 8, the ferromagnetic material forms an elongated body with an approximately rectangular cross section passing through the geometric axis of the movable stator. In this embodiment, the movable stator may additionally have paramagnetic parts that complement the shape of the movable stator to a regular cylinder.

Figures 3, 5, 7, 9, 11, 13 and 15 show the magnitude of the magnetic field in the middle of the rotor channel between the magnets of stator 1 and the movable stator 6. The graphs show the dimensionless magnetic field along the contour A-E-A , as the field for a movable stator 6, made of paramagnets, is assumed to be 1.0, ie 100%. When paramagnetic and ferromagnetic materials are used in the movable stator 6, the magnetic field is not amplified but only redirected, but when permanent magnets are used in the movable stator 6, the magnetic field increases with the magnitude of the magnetic field generated by these magnets. Depending on the design of the machine, the gain is different and depends on the ratio between the magnetic fields generated by the stator 1 and the movable stator 6. In the illustrated embodiment, the total magnetic field of the DC motor variant of Figure 14 is up to 150% stronger than the variants without additional magnets, ie the motor of figure 14 is 2 to 2.5 times more powerful than the variants shown in figures 2, 4, 6 and 8. The gain by using additional permanent magnets in the movable stators 6 depends from the specific parameters of the machine and cannot be summarized for all types of machines having different sizes and designs and using different materials. Common is the amplification of the magnetic field due to the addition of an additional magnetic field created by the permanent magnets of the movable stators 6.

The separation of the rotor 2 and the movable stator 6 leads to a number of effects that improve the performance of electrical machines. The rotor 2 is hollow because its interior is occupied by the movable stator 6 and therefore has a smaller mass. This provides less machine load, lower rotor inertia, shorter response time and easier machine start-up, ie better dynamic performance.

The magnetic field is formed in the area between the stators, where the rotor 2 is located and this allows better direction and concentration of the magnetic lines. This allows the movable stator 6 not to be cylindrical, since the direction of the magnetic field is known in advance and it is not necessary to conduct a magnetic field in all

BG 67304 Bl directions and therefore cavities can be left where a magnetic field is not required. The machine becomes lighter. In the examples shown, the movable stator 6 is flat because there are only two poles of the stator magnetic field.

When permanent magnets are inserted in the movable stator 6, the magnetic field in the rotor zone is a vector sum of the magnetic fields of the stator 1 and the movable stator 6. Since the movable stator 6 always orients in the same way to the magnetic field of the stator 1, the magnets of the movable stator 6 will always increase the total magnetic field to which the output power of the machine is directly proportional, ie. when using the same materials, the machine has improved output power / dimensions and output power / weight ratios. Or similar parameters of existing machines can be achieved using weaker and cheaper magnets.

Like the compass needle, the movable stator 6 self-orients itself according to the magnetic lines of the magnetic field generated by the stator 1. Depending on the type of machine, the movable stator 6 can rotate or be stationary relative to the housing of the electric machine. For example, in an induction motor, the movable stator 6 rotates at the angular velocity of the magnetic field generated by the stator windings of the fixed stator 1, i.e. faster than the rotor. In a DC motor, the movable stator 6 will remain stationary and will be affected by the displacement of the magnetic field generated by the current in the rotor windings 2, but the techniques to improve the operation of the motor and avoid sparking will only affect the equilibrium position of the movable stator 6, but not at its angular velocity, which will be zero after reaching a set mode. Regardless of whether the movable stator 6 rotates or not, it does not move relative to the magnetic field of the machine and does not over-magnetize - the losses and heating of the machine are reduced and the efficiency is increased. Since the movable stator 6 does not move relative to the magnetic field of the machine, no eddy currents are generated in it - heating is reduced and the machine can operate at higher speeds. Avoiding eddy currents simplifies the construction of the machine and hence its cost.

The magnetic field is formed in the area between the stators 1 and 6, where the rotor 2 is located and this allows better directing and concentration of the magnetic lines. The movable stator 6 may not be cylindrical, as the direction of the magnetic field is known in advance. It is not necessary to conduct a magnetic field in all directions and therefore cavities can be left where a magnetic field is not needed, respectively the machine becomes lighter.

The intensity of the magnetic field depends on the distance between the stators and not on the diameter of the rotor, because it is created between the two stators, ie it can work even with an infinitely large diameter, which is a linear motor. The magnetic field is created between the two stators and more complex shapes of the magnetic field can be generated because it avoids scattering in the central part of the currently existing machines. There may even be an odd number of poles.

It will be apparent to those skilled in the art that various variations and modifications of electrical machines are possible, which also fall within the scope of the invention as defined in the appended claims. The individual parts of the machine can be replaced with technically equivalent elements.

The reference numbers of the technical features are given only for the purpose of increasing the comprehensibility of the claims and therefore, these reference numbers have no restrictive effect on the interpretation of the elements indicated by these reference numbers.

Claims (1)

Electric machine comprising a fixed stator (1) fixed to the housing (4) of the machine, wherein the fixed stator (1) includes built-in permanent magnets (10) or stator windings, a rotor (2) fixed to a shaft (3) capable of free rotation relative to the fixed stator (1), wherein the machine uses magnetic induction to transfer energy between the stator and the rotor, wherein the rotor (2) is hollow and includes windings (11), characterized in that the electric machine includes at least an additional movable stator (6) located coaxially in the hollow rotor (2) and mounted by bearings (5) to the rotor (2) or to the shaft (3) with the possibility of free and independent rotation with respect to the axis of rotation of the rotor 2) and the shaft (3), said at least one additional movable stator (6) being made at least in part of ferromagnetic materials, and the fixed stator (1), the rotor (2), said at least one additional movable stator (6) and the shaft 3) are placed in each other and separated by gaps (14, 15, 16), wherein the rotor (2) is located between the fixed stator (1) and at least one movable stator (6)